Requirements for multi-purpose controls (joysticks)

Project No. BGAG 0100

Status:

completed 05/2002

Aims:

Multi-purpose controls (joysticks) are increasingly being used on earthmoving machinery for the control of safety-related functions. Buttons on the controls are used for user-friendly switching between different groups of functions. The result is that the control unit as a whole houses an increasing number of discrete functions which are grouped to form units and may be accommodated on several layers. The key question of the project was to establish the number of function units assigned to a multi-purpose control which a trained machine operator may cope with whilst still being able to operate the machine safely and reliably, even under hazard conditions.

Activities/Methods:

The above issue was addressed by means of video footage of joystick operation on wheel loaders and excavators on construction sites and during demonstrations at manufacturer's sites, surveys of machine operators, measurements of pulse rate and upper limb activity as well as measurements of the ambient parameters at the workplace.

Results:

The most significant results of the study are: The function units should be restricted to the basic movements and a further four additional function units per multipurpose control. The function on the multi-purpose control should be assigned to the machine's response in observance of compatibility rules. The control unit itself and the controls which it houses should be of ergonomic design, for example with adaptation of the geometry to the fingers and hand by the provision of a rest for the edge of the hand and/or forearm. The arrangement of the controls on the control unit and the assignment of functions to them should be standardized in consideration of frequency of use and risk potential presented by the functional units.